The following publications and patents describe AC supply systems, uninterruptible power supplies, parallel operation of AC generators, and other aspects related to the present invention:                (1) Chandorkar, M. C., et al., “Control of Parallel Connected Inverters in Standalone ac Supply Systems,” IEEE Transactions on Industry Applications 29(1):136–143, January/February 1993.        (2) Chandorkar, M. C., et al., “Novel Architectures and Control for Distributed UPS Systems,” APEC '94 Ninth Annual Applied Power Electronics Conference and Exposition, IEEE Power Electronics Society, the IEEE Industry Applications Society, and Power Sources Manufacturers Association, Orlando, Fla., Feb. 13–17, 1994, pp. 683–689.        (3) U.S. Pat. No. 5,596,492, issued Jan. 21, 1997, to Divan et al., “Method and Apparatus for De-Centralized Signal Frequency Restoration in a Distributed UPS System.”        (4) U.S. Pat. No. 6,118,680, issued Sep. 12, 2000, to Wallace et al, “Methods and Apparatus for Load Sharing Between Parallel Inverters in an AC Power Supply.”        (5) U.S. Pat. No. 5,436,512, issued Jul. 25, 1995, to Inam et al., “Power Supply with Improved Circuit for Harmonic Paralleling.”        (6) U.S. Pat. No. 6,169,669, issued Jan. 2, 2001, to Choudhury, “Digital Signal Processor Controlled Uninterruptable Power Supply.”        (7) U.S. Pat. No. 5,483,463, issued Jan. 8, 1996, to Qin et al., “Uninterruptible Power Supply (UPS) and Method.”        (8) U.S. Pat. No. 6,297,977, issued Oct. 2, 2001, to Huggett et al., “Parallel Operation of Multiple Generators.”        (9) J. David Irwin (editor-in-chief), Industrial Electronics Handbook, CRC Press/IEEE Press (1997), particularly 263–273 and 367–376.        